Association of Myocardial Enzyme Abnormality with Clinical Outcomes of Patients with COVID-19: A Retrospective Study

Background It has been observed that COVID-19 may cause myocardial damage, but there are few detailed reports on myocardial enzyme abnormalities. Methods In this retrospective study, we analyzed data from 157 consecutive laboratory-confirmed and hospitalized COVID-19 patients from Wuhan. We collected information on demographic and clinical characteristics, laboratory findings, and clinical outcomes. Logistic regression analysis was used to explore the risk factors associated with the severity of COVID-19. The association between myocardial enzyme abnormalities and the mortality was also investigated. Results The mortality in abnormal myocardial enzyme group was obviously higher than the normal group (P < 0.001). The majority of patients (n = 72, 97.3%) with normal cardiac enzyme group were of the common novel coronavirus pneumonia (NCP) type, whereas half of the patients with cardiac enzyme abnormalities (n = 40, 48.2%) developed critical and severe NCP type. The multivariable logistic regression analysis indicated that COVID-19 patients with increasing age (P = 0.035), higher levels of CRP (P = 0.038), and TNI (P = 0.036) were associated with increased death than other patients. Conclusions Myocardial enzyme abnormality and myocardial injury were associated with the severity and fatal outcomes of COVID-19. Clinicians should pay attention to the markers of myocardial injury in COVID-19 patients, especially those with older age, comorbidities, and inflammation.


Introduction
Coronavirus disease 2019 (COVID-19) is still a big challenge for public health and medical care. Previous studies have reported the general clinical characteristics of hospitalized patients with COVID-19, including signs, symptoms, imaging features, laboratory findings, therapeutic strategies and effects, and multiple organ dysfunction [1,2]. With the increase of confirmed cases and the accumulating clinical data, the cardiovascular manifestation caused by COVID-19 has attracted great attention. Huang et al. reported that 12% of patients had COVID-19-associated acute myocardial injury (AMI), manifested by elevated levels of high-sensitive troponin I 1 . In a report on 138 patients with COVID-19, 16.7% had arrhythmias, and 7.2% had AMI [3]. The American College of Cardiology clinical bulletin has highlighted the cardiac implications of COVID-19 [4]. Thus, special medical attention should be paid to cardiac functionrelated indicators of COVID-19 patients. Myocardial enzymes are important indicators for judging myocardial function [5]. Even if there is no deliberate detection for myocardial enzymes, LDH and CK are often included in blood biochemical tests. However, to date, specific information characterizing whether patients with COVID-19 with myocardial enzyme abnormality face greater risk and have worse in-hospital outcomes remains unclear. The present study investigated the association of myocardial enzyme abnormality with fatal outcomes of patients with COVID-19.

Study Population. This study was approved by the institutional ethics board of the Union Hospital of Huazhong
University of Science and Technology (Wuhan, China). Writing informed content was waived because it is a retrospective study. 157 consecutive patients with laboratoryconfirmed COVID-19 admitted to Union Hospital of Huazhong University of Science and Technology between January 12, 2020, and February 26, 2020, were included in this retrospective cohort study. Patients with COVID-19 were diagnosed and classified as common or severe type according to the World Health Organization interim guidance. The cases without cardiac markers were excluded.

Data
Collection. Data on demographic and clinical characteristics (age, sex, and symptoms), underlying comorbidities, laboratory findings, and cardiac markers, were collected from the electronic medical records. Laboratory test results including blood routine tests, coagulation profiles, blood glucose and lipids, inflammatory markers, and cytokine, liver, and renal function were recorded and compared. Cardiac markers measured on admission were collected, including cardiac troponin I (TNI), creatine kinase (CK), lactate dehydrogenase (LDH), and creatine kinase-myocardial band (CK-MB). Cardiac injury was defined as serum levels of TNI above the 99th-percentile upper reference limit (>26.2 μg/L). All data were independently reviewed and entered into the computer database by 2 analysts (Q.Z. and Z.Z.). Patients were categorized according to the presence or absence of myocardial enzyme abnormality and myocardial injury. The clinical outcomes (i.e., discharges and mortality) were monitored up to February 26, 2020.
2.3. Statistical Analysis. Statistical analysis was performed using SPSS version 26.0 (Armonk, NY; GraphPad version 7.00, San Diego, CA). Continuous variables were presented as median (interquartile range (IQR)) and mean (standard deviation (SD)) for nonnormally distribution and normally distribution, respectively. Categorical variables were presented as n (%). Mann-Whitney U test or χ 2 test was used to compare differences between presence and absence of myocardial enzyme abnormality or myocardial injury where appropriate. To explore the risk factors associated with myocardial enzyme abnormality and myocardial injury, univariable logistic regression analysis, Pearson's correlation analysis, and Spearman's rank correlation analysis were used for binary variables, normal distributed continuous variables, and nonnormal distributed continuous variables, respectively. To explore the risk factors associated with in-hospital death, univariable and multivariable logistic regression models were used. Considering the number of deaths (n = 18) in this study and to avoid collinearity between variables and overfitting in the model, five variables were selected for multivariable analysis based on previous findings and clinical constraints.

Demographic and Clinical Characteristics.
A total of 331 consecutive COVID-19 adult inpatients (18 years old) in the medical record system were screened initially from January 12, 2020, to February 26, 2020. Patients without available medical information and missing core results of laboratory examination (TNI, CK-MB, LDH, and CK) and duplicated records were excluded. Ultimately, 157 patients were included in the final analysis.

Disease Markers
However, there is no significant difference in creatinine, uric acid, total cholesterol, triglyceride, and low-density lipoprotein cholesterol between the two groups.

Clinical
Outcomes. In our study, a total of 18 patients (11.5%) died, and the rest (139 (88.5%)) were recovered and discharged as shown in

Discussion
Previous study has found that the novel coronavirus may attack many important organs [6]. Heart and myocardial injury might be involved and even be regarded as one of the leading causes of death of COVID-19 patients [7]. However, few studies concentrated on the effect of COVID-19 infection on the heart, and the degree of myocardial damage  Disease Markers on the clinical outcome and prognosis remained unclear. Therefore, our study performed a retrospective analysis to report the association between cardiac abnormalities including elevated myocardial enzyme levels (52.87%) and myocardial injury (11.46%) and fatal outcomes of patients with COVID-19. According to a recent study of Wuhan city, severe cases of COVID-19 were independently associated with older age, elevated levels of hs-TNI, CK-MB, and myohemoglobin [4]. It was notable that a previous report in 138 COVID-19 patients found that 7.2% of patients had cardiac injury [3], which was confirmed by another report in 187 patients with COVID-19 indicating 27.8% of patients exhibited myocardial injury as indicated by elevation of cardiac troponin T levels [8]. Besides, in 2003, a study from Guangzhou institute of respiratory diseases showed that CK-MB and LDH increased in 10.8% and 16.0% of patients with severe acute respiratory syndrome (SARS), respectively [9]. These observations suggested that myocardial injury and abnormal cardiac enzymes played greater roles in the fatal outcomes of COVID-19 patients. In our current study, of the 157 patients with COVID-19, 83 showed abnormal cardiac enzymes, and 18 exhibited myocardial injury. In abnormal cardiac enzyme group, both the mortality rate and proportion of severe cases were higher than the normal group. Compared with patients without myocardial injury, patients with myocardial injury presented with more severe NCP type (72.2% vs. 31%), more cardiovascular disease (CVD, 33.3% vs. 13.8%), and higher mortality rate (61.1% vs. 6.9%), manifested by abnormal laboratory findings, such as older age, higher levels of CRP, ESR, SAA, IL-6, TNI, AST, ALP, and urea nitrogen, demonstrating that cardiac injury in COVID-19 patients was associated with major adverse clinical outcomes.
Cardiac complications, including abnormal cardiac enzymes, cardiac injury, heart failure, and arrhythmias, were common in patients with pneumonia. Risk factors of cardiac events after pneumonia usually include older age, coexisting cardiovascular diseases, inflammatory, and severity of NCP type. Similarly, Chen reported that in critical and severe patients with COVID-19, the markers of myocardial injury and inflammation including TNI, N-terminal probrain natriuretic peptide (NT-proBNP), and high-sensitivity CRP were significantly elevated and associated with mortality [10]. Increased age, even male sex, hypertension, and coronary heart disease were additional risk factors leading to severity of pneumonia. Consistently, our study indicated that older age, coexisting diseases, especially for CVD, inflammatory, TNI levels, and function of the liver and kidney were possible risk factors of COVID-19 patients, which were also in associated with myocardial injury.
Previously study believed that increased age was an important independent factor of mortality in MERS and SARS [11,12]. Our study also identified that older age was associated with cardiac injury and death of COVID-19 patients. Because of elderly patients with poor immunity, especially the lower function of T lymphocytes and multiple comorbidities, the inflammatory cytokines such as IL-6 and TNF-α would be abnormally elevated contributing to cytokine storms, and they were more likely to develop into severe pneumonia potentially leading to poor outcome when infected with virus as compared to young patients.
In addition, large studies reported that CVD was a risk factor for COVID-19 patients [13,14]. A study of 1099 COVID-19 patients demonstrated that the proportion of patients had coexisting disease reached to 23.7% and hypertension (15%), diabetes (7.4%), and coronary heart disease (2.5%) were the top three underlying diseases [13]. Supporting this point of view, our current study indicated that patients with underlying CVD and other comorbidities were more likely to develop abnormal cardiac enzymes, elevated TNI levels, and more severe NCP type.
It is notable that a recent report on 112 patients hospitalized with COVID-19 who have experienced a definite outcome found that most of patients had normal levels of TNI at the beginning of infection while 37.5% patients increased during hospitalization, especially in those with severe clinical conditions [15]. In a similar study of 138 patients, 36 patients required ICU admission, and their levels of CK-MB and hs-TNI were significantly higher than the non-ICU group [3]. Further, previous study also reported that levels of cardiac troponin and myoglobin in the severe and death group were prominently elevated than the mild and discharge group [16,17]. Particularly, in our present study, 23.68% of patients showed elevated TNI levels and also had a markedly odd ratio of 1.018 (95% CI (1.001-1.035)) for the risk of myocardial injury and death triggered by COVID-19. Moreover, other indicators of cardiac injury including CK and LDH were also independent risk factors of COVID-19 death. Thus, it was rational to resume that the elevation in cardiac TNI could be a warning sign for the death of patients with COVID-19 which should be evaluated and paid more attention to in clinical practice.
The potential mechanism of COVID-19-induced myocardial injury was not well known so far. Some researchers believed that inflammatory response might be at least partially responsible for cardiac injury. A recent report on 416 patients found that markers of inflammatory response, such as CRP, procalcitonin, and leukocytes, were significantly increased among patients with cardiac injury [4]. Chen et al. also reported that patients with COVID-19 who suffered from more severe pneumonia had higher levels of IL-6 and other inflammatory cytokines [10]. In our current study, we found that high levels of myocardial injury markers were significantly in association with increase of white blood cells and neutrophils and decrease of lymphocytes in patients with abnormal cardiac enzymes, which were consistent with other COVID-19 studies. Moreover, other inflammatory cytokines including CRP, IL-6, ESR, and SAA were also elevated. The release of these inflammatory cytokines could lead to myocardial inflammatory cell infiltration and inflammatory storm, which would contribute to increase of myocardial cell apoptosis and necrosis. Supporting our point of view, in a retrospective study of 463 cases of COVID-19 patients, researchers found that severe and aged COVID-19 patients suffered more obvious decreases in total lymphocytes, CD4 + , and CD8 + T lymphocytes, suggesting SARS-CoV-2 infection might affect heart by inflammation and cytokine storm [18]. Collectively, we 7 Disease Markers speculated that severe inflammatory response might be a possible mediator of myocardial injury caused by COVID-19. Therefore, early and special anti-inflammatory treatment should be undertaken in clinical.
Another mechanism for COVID-19 caused myocardial injury might be associated with angiotensin converting enzyme 2 (ACE2). Studies reported that ACE2 had strong binding affinity to the spike protein of SARS-CoV-2 and could contribute to myocardial inflammation and damage [19]. SARS-CoV virus RNA was detected in human heart samples, indicating SARS-CoV-2 might directly attack heart by binding ACE2 on myocardial cells [20]. The expression of ACE2 protein in heart samples was markedly downregulated by invasion of SARS-CoV-2 virus, which not only caused impaired endothelial function, elevated blood pressure, and reduced myocardial contraction force but also increased the angiotensin II. Finally, increased oxidative stress, inflammation, and fibrosis in heart were occurred by activating TGF-β and MAPK pathways [21]. So far, the use of ACEI/ARB in COVID-19 patients remained controversy. A large study of 1178 cases in Wuhan suggested that ACEI/ARB were not associated with the severity or mortality of COVID-19 patients with hypertension [22]. Therefore, we might conclude that for COVID-19 patients who previously used ACEI/ARB, the use of these drugs might not need to be discontinued based on the current data.
Our study had several limitations. Firstly, only 157 patients with confirmed COVID-19 were included, and the number of patients with elevated TNI levels was limited. Therefore, a larger cohort was needed to verity our conclusions. Secondly, some information about myocardial injury, such as echocardiography, electrocardiogram, and NT-proBNP levels, was not presented in the study because the data was incomplete partly due to the limited conditions of extraction. Thirdly, the mechanism of potential myocardial injury and inflammation caused by COVID-19 was not specific, which required more evidence from the long-term observation and prospective study design. Our present findings might provide clinicians with some evidence to pay attention to the cardiac pathology in future especially for patients with elevated cardiac enzyme levels on admission.

Conclusions
Myocardial injury was associated with the severity and fatal outcomes of COVID-19. SARS-CoV-2 virus might attack heart by inducing inflammatory storm or binding with ACE2. Clinicians should pay attention to the markers of myocardial injury in COVID-19 patients, especially those with older age, comorbidities, and inflammation. Finally, early and special anti-inflammatory or myocardial protection treatment should be undertaken for patients with COVID-19 in clinical.

Data Availability
The data used to support the findings of this study are available from the corresponding author upon request.

Conflicts of Interest
The authors declare no conflicts of interest.